additional compiler options are not appended when compiling qtvars_plugin_import.cpp

Steps to reproduce:

Create new console project using the wizard.
Change C++ Language Standard to ISO C++17 in project properties.
Add /Zc:__cplusplus in Additional Options of the project properties.
Compile.

I get an error on compilation of `qtvars_plugin_import.cpp`:

fatal error C1189: #error:  "Qt requires a C++17 compiler, and a suitable value for __cplusplus. On MSVC, you must pass the /Zc:__cplusplus option to the compiler."

I tried adding other stuff to additional options and then I've enabled verbose output of msbuild. I can see those options correctly passed to compilation of all source files except `qtvars_plugin_import.cpp`. It gets none of them. It's a generated file and I don't see any way to pass those options to it.